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Gas Furnace Buying Guide

gas furnace buying

Purchasing a new furnace is not something homeowners do often. We understand that there are a lot of options and it may be confusing. If you have an older furnace you may want to consider replacing it with a more efficient model. Especially if you intend to stay in your home for years to come consider upgrading to improve the comfort of your home. Below is a gas furnace buying guide to help you navigate the process when you are purchasing a new furnace.


The size of the furnace affects the comfort of your home, efficiency and how long the furnace will last. The furnace size must be the right fit for the heating needs of your home. If a furnace is sized too small for your home, then it will not properly heat the home and increase your energy bills. If your heater is sized too big for your home, then the efficiency will decrease, the lifespan of the furnace will decrease and you will be uncomfortable. This is not something you will need to figure out on your own. A professional can analyze the heat needs of your home using Manual J load calculation to ensure you purchase the right size for your home.

Burner Options

Single Stage Furnaces

The most common burner option is single stage. This type of furnace has only two operating modes on or off. A single stage furnace always produces heat and moves air on high output regardless of conditions inside or outside of home. This leads to inefficient operation, decreasing comfort and higher energy bills.

Two-Stage Furnaces

A two-stage furnace allows the furnace to operate at two different settings high or low. The low setting allows the furnace to operate a lower capacity. This will allow the furnace to better match heating requirements in milder weather. This leads to a more comfortable home and a lower fuel bill. The two option furnace provides a more quiet operation, a more comfortable home, more air filtration and less strain on the furnace.

Modulating Furnaces

Like single and two stage furnaces modulating furnaces have a low and high setting but can also operate at any point in between. Modulating furnaces constantly monitor and adjust their output to account for any changes. By doing so they are able to eliminate large temperature swings.

Blower Options


A multi-speed blower allows the installer to select a speed for heating, cooling and fan operation. This type of blower does not account for any changes in operation such as dampers being opened or a clogged filter.

Variable Speed

An installer also sets the operating conditions for a variable speed blower. However, instead of picking the speed to provide a specific air flow rate desired the variable speed often corresponds to a specific air flow rate. The furnace adjusts to changes in conditions to provide optimal comfort.


The efficiency of a furnace is measured as a percentage by the AFUE rating. This rating reflects how efficiently a furnace converts gas into heating energy. The AFUE can range between 80% to 97%. The higher the number the more heat it can output from each therm of gas. Simply put, a furnace with an 80% AFUE turns 80% of it’s energy into heat, meaning 20% goes to waste. A higher efficiency furnace will convert almost all its energy into heat. A high efficiency furnace will cost more upfront, so consider your budget when deciding. It is also a good idea to compare installation costs and long-term efficiency savings. Keep in mind that the AFUE does not accurately reflect the efficiency of the furnace once installed. The actual efficiency of the furnace will be impacted by installation, duct sealing, insulation and routing as well.

Gas Furnace Features

Depending on the furnace price, each brand of furnace offer similar features. Some examples of features that make a furnace more efficient are variable-speed blowers, variable heat output and dual heat exchangers. Other features of gas furnaces include advanced air filtration options and zoned heating systems. Keep in mind that zoning is more useful for larger homes rather than smaller homes.

We know there is a lot of information out there. Contact us online or give us a call at 818-341-3406 so we can assist you in finding a furnace that best fits your needs. To learn more about services LA Construction Heating and Air offers, please visit our homepage.

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